Re: [Amel Yacht Owners] Re: Prop Shaft Electrolysis


I posted a schematic of the isolated ground for the engine in the files section, Jamie.

On Dec 3, 2015, at 6:15 PM, James Wendell ms42phantom54@... [amelyachtowners] <amelyachtowners@...> wrote:


Well, actually I do understand the concept of isolated ground, but I was not aware that Amel would go to the trouble of installing relays to break the DC wiring to the engine when it is shut down. There is no mention of that in any of my Amel schematics, but since I am new to this boat I still have things to learn.

And by the way, I hope I did not promote US standards as if they should be the world standard. I wish the US were on the metric system, for example, but please don't let me rant on about that one. I also wish we used single phase 230 volts like most of the rest of the world (at least Europe). There are many regs in the US that I disagree with, but electrical safety is a fairly strong one. I can see the benefit of an isolated ground from the perspective of galvanic corrosion control, but I still question the overall safety of such systems, particularly when it comes to AC earth connections.

Anyway, I have not yet selected the engine brand I will install. The easiest solution (but least desirable based on my recent disaster) would be a replacement Volvo Penta D3-110, third generation of course. That would maintain the existing systems as they are, including the isolated ground. Any other brand would have to be carefully evaluated to ensure total compatibility and to maintain the Amel way of life.

I will go check on that isolated ground everyone is talking about. Very interesting indeed.

Thanks again,
s/v Phantom Amel 54

On Thursday, December 3, 2015 2:56 PM, "'Bill & Judy Rouse' yahoogroups@... [amelyachtowners]" <amelyachtowners@...> wrote:


Isolated ground is probably not something that you learned in electrical engineering school, but it is an important thing to understand in a marine environment. Amel uses an isolated ground system where the DC negative IS NOT part of the engine frame. You will notice this with the temperature sensor and other sensors. Most marine engines have a single wire going to the temperature sensor because the engine is ground. Your Amel has an isolated ground and there will be two wires. The only time the DC negative is connected to the starter is when the start switch is turned to start.

Your alternators will also be isolated ground alternators. I know a Bavaria owner who failed to install the correctly grounded alternator and his entire saildrive became a sacrificial chunk of metal.

As to what ABYC thinks is important, I am not so sure. Just because they are American, does not mean they are right. I would argue a number of their publications, but that is for another day and another subject.

Good luck with your new engine...did you state what engine you plan to use?

BeBe 387

On Thu, Dec 3, 2015 at 7:35 PM, James Wendell ms42phantom54@... [amelyachtowners] <amelyachtowners@...> wrote:
Eric, I guess I don't understand what you mean. How does the negative get disconnected after the generator starts? It would have to be connected in advance to get the starter to even work. Most negatives go directly to the generator frame which is integral with the starter.
Can you help me here?
s/v Phantom

On Thursday, December 3, 2015 1:06 PM, "sailormon kimberlite@... [amelyachtowners]" <amelyachtowners@...> wrote:

My generator has an isolated ground and the negative is not connected to the start battery except when the generator is starting.
Fair Winds
Kimberlite Amel Super Maramu #376
From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Thursday, December 03, 2015 9:41 AM
To: amelyachtowners@...
Subject: Re: [Amel Yacht Owners] Re: Prop Shaft Electrolysis
Kent, again thanks for the kind words about my engine failure on Phantom. Just to confirm my comments, I am not suggesting the exhaust des ign was necessarily at fault, but in my case the layout of the system certainly could have exacerbated my engine failure. In any event, if I can take steps to improve with my new engine, I will.
If I can comment on your AC findings, I understand that Amel deliberately does not connect the AC earth to the DC bonding grid. That, of course, is totally opposite from US regulations that mandate that connection for safety, a practice to which I fully subscribe as an electrical engineer. There is also the absolute "no-no" of connecting AC neutral to earth anywhere on the boat unless you have an isolation transformer.
The exception, however, is at a separately-derived power source. For a shore power connection, the neutral-to-earth bond would be at the shore power source in the marina. For a generator, it would be at the generator. When the automatic transfer switch (ATS) is in shore power mode, it ensures the neutral is connected only to the shore power feeder and not the boat. It also ensures the grounding systems are not interconnected, since the neutral is not connected to the boat systems. Further the generator case will be connected to earth, since the battery negative for the starter lands on the frame. When the ATS is switched to generator, the neutral "should" be tied to AC earth, since it "should" be bonded to PE at the generator. You should verify the connection between the blue neutral wire and the green/yellow PE. If it is connected you are safe; if not, and you had a fault in an AC circuit to earth, the neutral would not have a return path to its source and the AC current would try to find an alternate path - not good.
Many don't I know, but technically an inverter is a separately-derived power source, and the neutral there should be tied to earth as well. The problem is that most inverters also function in pass-through mode.
I hope that helps. Let me know what you find.
s/v Phantom Amel 54
On T hursday, December 3, 2015 7:42 AM, "karkauai@... [amelyachtowners]" <amelyachtowners@...> wrote:
Well, I have separated all the 220AC ground wires at the 220 box in the galley and at the 220 boxes in the engine room. I found that the output cable from the generator is grounded to the generator case, and thus, to the bonding system. The other end of that cable goes to the automatic switch that chooses generator over shore power, where it is connected to all other 220 grounds via the output from the switch.
This violates my understanding that the 220AC ground should NOT be connected to the bonding system. Now what????


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